1. Field of the Invention
The present invention relates to a reciprocatory piston type displacement compressor, such as a swash plate type constant displacement compressor having a swash plate mechanism on a drive shaft for reciprocating pistons in a plurality of axial cylinder bores disposed around the drive shaft, and a wobble plate type variable displacement compressor having an assembly of a rotatable drive and non-rotatable wobble plates on a drive shaft for reciprocating pistons in a plurality of cylinder bores disposed around one end of the drive shaft, to thereby compress a refrigerant in the cylinder bores.
2. Description of the Related Art
Generally, a swash plate type constant displacement compressor, such as the multi-cylinder swash plate type compressor disclosed in U.S. Pat. No. 4,534,710 to T. Higuchi et al., has a rotatable swash plate on a central drive shaft, double head reciprocatory pistons, each being disposed to straddle the periphery of the swash plate, and a plurality of cylinder bores formed in axially combined cylinder blocks to be disposed around the drive shaft in such a manner that the bores in the combined cylinder blocks are mutually axially aligned with one another to thereby receive the reciprocatory pistons.
A wobble plate type variable displacement compressor such as the variable displacement wobble plate type compressor disclosed in U.S. Pat. No. 4,688,997 to S. Suzuki et al., usually has a non-rotatable wobble plate on a central drive shaft, single head pistons connected to the wobble plate, and a plurality of cylinder bores formed in a cylinder block to be disposed around one end of the drive shaft to permit reciprocation of the pistons in the cylinder bores.
Due to an increasing demand for a compact but large displacement compressor the current main stream is a multi-cylinder compressor having five or more cylinder bores disposed around an axial drive shaft supported in the center of the compressor.
In the above-described reciprocatory piston type compressors, a fluid i.e., a refrigerant gas, is compressed in each cylinder bore and flows through a discharge port of a valve plate juxtaposed to an opening of the cylinder bore. The compressed refrigerant gas then pushes and opens a discharge reed valve to enter a closed discharge chamber defined in a cylinder head of the compressor.
The cylinder bores are circumferentially arranged at equal and relative small intervals in a cylinder block or blocks of the compressor. Therefore, before one discharge reed valve, which has been opened to permit the compressed refrigerant gas to be discharged from the cylinder bore, is restored to the closed position, an adjacent discharge reed valve is opened by the refrigerant gas compressed in the corresponding cylinder bore. Namely, an overlapping of the opening of two adjacent discharge reed valves occurs.
Since the discharge chamber is provided as a simple closed space for collecting the compressed refrigerant gas discharged from the respective cylinder bores and sending it toward the outside refrigerating circuit of the compressor, when the two different flows of the refrigerant gas discharged from the two adjacent currently open discharge ports enter the discharge chamber, the two flows of the compressed refrigerant gas generate fluid pressure waves which interfere with each corresponding respective flow within the discharge chamber. As a result, a problem arises in that this interference amplifies the pulsation of the discharged refrigerant gas before the compressed refrigerant gas flows into the outside refrigerant circuit. Also, a pressure difference always exists between the two adjacent currently open cylinder bores, and thus a refrigerant discharged from a later opened bore among the open cylinder bores may flow back into another cylinder bore which is to be closed, to lower the displacement efficiency of the compressor. Further, when each discharge reed valve is at a position just before a closure thereof, the valve is subjected to the complex actions of discharge pressures acting on both the upper and lower faces thereof, to thus aggravate the vibration of the reed valve.